Conventionally, in the data processing system wherein the host and the disk array apparatus is connected through the channel for communication, generally, the host issues and transmits CCW (channel command word) to the DKC to make the DKC perform the command processing. Particularly, the host issues and transmits a CCW chain to the DKC in order to make the DKC continuously perform processing operation and jobs between the host and the DKC. The CCW chain has various kinds such as a CCW chain for controlling the data write to the storage unit such as a HDD (hard disk drive).
In a configuration example of the conventional data processing system as show in FIG. 8, a host 901 issues a plurality of CCWs 801 as a CCW chain 802 and transmits them to a DKC 902 in a disk array apparatus 900 to make the DKC 902 process a CCW chain 804 and a CCW 805. For example, the host 901 issues the CCW chain 802 as shown in FIG. 9 to make the DKC 902 perform one processing operation and job. When the CCW chain 802 is processed between the host 901 and the DKC 902, an IP 111 creates the CCW chain 802 in a MS 112 in the host 901. A CH 113 transmits the CCW chain 802 as a frame 803 of the CCW 801 to a PORT 121 of the DKC 902. The frame 803 of the CCW 801 is received at the PORT 121 of the DKC 902 so that the CCW chain 804 is obtained by the DKC 902. A CP 123 sequentially processes each CCW 805 constituting the CCW chain 804. The PORT 121 transmits response status of the processing result of the CCW 805 to the CH 113.
The CCW 801 and the CCW 802 issued from the host 901 may include, for example, a search condition. The search condition is information of the condition for a search processing performed in the DKC 902. The DKC 902 performs the search processing to the CCW 805 according to the search condition. The result of the search processing is returned to the host 901 as a response status. The search processing is, for example, performed in order to check whether or not the value in the memory area of the DKC 902 is matched with the value for the search condition. The host 901 determines the CCW 801 to be issued subsequently based on the state of the CCW 801 including the search condition in the DKC 902 and the response status from the DKC 902 according to the processing result.
Japanese Patent Application Laid-Open Publication No. 2001-125866 describes a technology for reducing an overhead in communication between the CPU and the DKC, namely a technology for batch processing of a plurality of CCWs and performing a recovery processing as in the independent processing even if the CCW is abnormally ended in the batch processing.